.BMP can be attached as an attachment bout won't display as an image. BMP is very antiquated file formate - you should be able to convert or "save as" a .jpg
"The native file format of the Windows platform is like the parent format to GIF, JPG and PNG. BMP formats commonly do not allow for image compression (i.e. large files). BMP images are crisp and precise, but being pixel dependent they don’t scale well. On the web, the detail comes at the cost of file size and that’s why you won’t see BMP images used on the web."
PS: As a non-subscribing member you can't delete your own threads or posts. One of the perks of being a subscriber is that for Bronze and higher you can delete your own posts. At silver and higher you can also delete your own entire threads (threads you start)